8o THE RUBBER INDUSTRY 



this class of rubber. Moreover, the number of men 

 comprised in the gangs formed to exploit the caucho 

 industry varies greatly from month to month, and this 

 adds to the difficulty of drawing up any statistics of a 

 reliable character. 



Experiments tried in 1913 with the gouge, working 

 on the herring-bone system for both forest-grown and 

 planted trees, showed that for the first three or four 

 weeks the average yield of latex per tree was double 

 that obtained with the machadinho, but the collector 

 tapped only one-half the number of trees daily. Doubt- 

 less this drawback would have been remedied to some 

 extent as the tappers became more expert ; but an out- 

 break of cambium disease occurred soon after the 

 experiments were commenced, and it was of such a 

 virulent nature that the work was abandoned. Another 

 objection to excision methods was that after the first 

 month the quality of the latex weakened even when the 

 trees were free from disease, and the conclusion reached 

 was that the additional milk extracted overtaxed the 

 general functions of the trees. These experiments were 

 carried out over a period of six months in the Madeira 

 and Purus districts to test thoroughly the possibility of 

 increasing the average yield by the introduction of 

 gouge tapping ; they were only relinquished in view of 

 the combined effects of cambium disease and the lower 

 quality of latex obtained. The trials were made at 

 some seventy different properties on the Madeira and 

 Purus, and they may be accepted, therefore, as conclusive 

 proof that any system of bark excision is unsuitable for 

 rubber-trees in the Amazon Valley owing to unexplained 

 atmospheric influences. 



